1. Field of the Invention
This invention relates to a process for in-situ, real-time fine delay adjustment of individual packaged surface acoustic wave (SAW) devices.
2. Brief Description of the Prior Art
In the surface acoustic wave art, there is a need for precision delay and narrow band filter requirements. Many systems, such as, for example, missile seeker subsystems, require multiple signal channels which amplitude and phase track over the military specification temperature range, usually -55.degree. C. to +100.degree. C. Compact IF filters in each of these channels must be of the highest performance and uniformity. Such filters must also amplitude and phase track to within 0.5 dB and 2.0 degrees, respectively across the 3 dB bandwidth.
Standard fabrication tolerances (metal thickness and electrode width) are unable to produce devices which meet these requirements. For post-mounted center frequency adjustment, several manufacturers deposit non-piezoelectric materials on the surface to slow the surface wave. These in-situ approaches are not applicable to device fabrication in which the SAW devices must track amplitude and phase responses over mil-spec temperature range, usually -55.degree. C. to +100.degree. C. Most deposited layers have temperature coefficients of delay which differ from the substrate. Hence these procedures are not applicable.